MAXIMIZING PERFORMANCE OF UV SYSTEMS FOR SMALL COMMUNITY DRINKING WATER DISINFECTION. Scott Bindner NC AWWA-NEA SPRING CONFERENCE April 13, 2015

Transcription

1 MAXIMIZING PERFORMANCE OF UV SYSTEMS FOR SMALL COMMUNITY DRINKING WATER DISINFECTION Scott Bindner NC AWWA-NEA SPRING CONFERENCE April 13, 2015

2 TREATING SMALL COMMUNITY DRINKING WATER Concerns with obtaining supplies/chemicals in remote locations Disinfection by-products Taste impacts from chlorine Operator experience These and other variables can lead to complexity when determine a course of treatment

3 TREATING SMALL COMMUNITY DRINKING WATER Complexity leads to rapid decision making 1. Default to traditional methods of treatment such as chlorine 2. Omission of treatment if water is considered to be of high quality

4 EXISTING STATE OF GROUNDWATER TREATMENT 65% of Groundwater Suppliers in the United States Provide Drinking Water WITHOUT Disinfection (Borchardt, 2012) 12% of Drinking Water in Europe is NOT Disinfected (Van der Hoek, 2014) 22.5% of Groundwater in Europe is NOT Disinfected (Van der Hoek, 2014)

5 WHY DISINFECT? CRYPTOSPORIDIUM Parasite that can live inside the intestines of humans/farm and wild animals/pets Forms protective shell (an oocyst) that enables it to live in harsh conditions Resistant to chlorine Milwaukee, WI ,000 sick, 104 deaths largest documented waterborne disease outbreak in US history Surface water treatment plants and groundwater providers under influence of surface water must monitor for Cryptosporidium

6 WHAT IS UV LIGHT? Ultraviolet (UV) light is invisible to the human eye UV is comprised of electromagnetic radiation of wavelengths ranging from 10 nm to 400 nanometers (nm) 200 nm to 280 nm are germicidal

7 HOW DOES UV DISINFECT? UV light penetrates the cell wall The UV energy permanently alters the DNA structure of the microorganism Cell Wall The microorganism is inactivated and unable to reproduce or infect DNA Nucleic Acid

8 UV DISINFECTION MECHANISM A C G T A A C A T G C A T T G T G C DNA Double Strand UV DNA A C G T A A C A T G C A T T G T Dimer G C Dimerization of Thymine Nucleotides

9 UV Dose (mj/cm 2 ) MULTI BARRIER APPROACH Adenovirus Chlorine Disinfection Dual Protection E.coli Rotavirus Poliovirus Hepatitis A Streptococcus Giardia Legionella Chlorine CT UV Disinfection Crypto

10 UV Dose (mj/cm 2 ) MULTI BARRIER APPROACH >186 mj/cm2 Adenovirus UV Disinfection Rotavirus Poliovirus Hepatitis A Giardia Crypto E.coli Streptococcus Legionella Chlorine CT

11 REASONS FOR USING UV Multi-barrier protection Protection against chlorine-resistant organisms (e.g. Cryptosporidium) Tool to reduce DBPs Meet virus treatment requirements (small systems) Use as primary disinfectant reduces CT and associated footprint Environmental contaminant treatment (ECT): Properly designed UV systems improve taste and odor, nitrosamines, other chemical contaminants

12 NEUSTADT, ONTARIO CANADA TROJANUV SWIFT SC

13 NEW YORK CITY - TROJANUVTORRENT

14 NEW YORK CITY 2.2 USBGD, 56 X 40 MGD REACTORS 14

15 TYPES OF UV LAMPS Three (3) distinct types of UV lamps used for municipal drinking water applications Low-Pressure (LP) Low-Pressure, High-Output (LPHO) Medium-Pressure, High-Output (MP) Characterized by the mercury vapor pressure inside the lamp, and the UV energy they produce

16 UV LAMP SUMMARY LOW PRESSURE LAMPS Low Energy Higher Efficiency More Lamps Required MEDIUM PRESSURE LAMPS High Energy Lower Efficiency Less Lamps Required UV users seek both high efficiency and low lamp count

17 TROJAN UV SOLO LAMP TECHNOLOGY Introduced in 2007 High efficiency low-pressure lamp, 254 nm output High-wattage lamp with highintensity Dose can be achieved with same contact time and fewer lamps Long lamp-life Up to 15,000 hours of operation Solo Lamp delivers both high efficiency and low lamp count

18 USING HIGH-EFFICIENCY LAMPS IN A SMALL UV SYSTEM Issue #1 Flow Jetting UV Chambers are often validated with 90 elbows installed at the inlet flange Inlet Pipe Elbow UV CHAMBER

19 USING HIGH-EFFICIENCY LAMPS IN A SMALL UV SYSTEM Issue #1 Flow Jetting Majority of flow enters at the bottom of UV chamber leading to significantly higher velocities when compared to the top of the chamber Low Velocity Zone Jetting Zone

20 USING HIGH-EFFICIENCY LAMPS IN A SMALL UV SYSTEM Issue #2 Absorbance Using fewer lamps results in challenges in ensuring effective distribution of light throughout UV chamber High intensities emitted by high-wattage UV lamps can lead to a scenario where a significant amount of UV is absorbed by steel walls.

21 USING HIGH-EFFICIENCY LAMPS IN A SMALL UV SYSTEM Issue #3 Sensor-Lamp Distance Validations using intensity set-point approach (DVGW) require high- and low-intensity test points. Test points ideally should generate a similar dose. Use of high energy lamps in a small chamber can result in test points having lower doses. Results in smaller flows and poorer performance during validation and in the field.

22 USING HIGH-EFFICIENCY LAMPS IN A SMALL UV SYSTEM Issue #4 Reflection Reflective materials such as aluminum or Teflon can be used to reflect UV light back through the water to increase performance. Fouling is unpredictable and there is no guarantee of long-term performance.

23 USING HIGH-EFFICIENCY LAMPS IN A SMALL UV SYSTEM Issue #4 Reflection Obtaining disinfection without reflection is the ideal way to ensure longterm performance

24 USING HIGH-EFFICIENCY LAMPS IN A SMALL UV SYSTEM SOLUTION Using high-powered lamps in a small chamber is prone to underperformance unless the flow can be modified. Computational Fluid Dynamic (CFD) testing of three approached to flow modification: 1. No Flow Tailoring 2. Inlet Flange Flow Modification (Cone-Shaped Baffle) 3. Flow Modification Throughout Chamber (Multiple Baffles)

25 CFD ANALYSIS Uses advanced mathematical equations to predict flow paths and simulate how water interacts with surfaces in a UV chamber With this software we can accurately predict UV exposure times and doses within a closed vessel

26 RESULTS No Flow Modification Velocity Profile

27 RESULTS No Flow Modification Dose Profile

28 RESULTS Inlet Flange Modification Velocity Profile

29 RESULTS Inlet Flange Modification Dose Profile

30 RESULTS Multiple Baffles Velocity Profile

31 RESULTS Multiple Baffles Dose Profile

32 CONCLUSIONS Areas of low velocity (outer chamber) receive low levels of UV intensity. Areas of high velocity (inner chamber) receive high levels of UV intensity. More UV energy is taken up by the water and absorbed by pathogens instead of the chamber wall. More particles receive a higher dose and more particles receive the same level of dose Use of multiple baffles also leads to improved mixing.

33 CONCLUSIONS More particles receive a higher dose while in the UV chamber

34 APPLICATIONS OF FLOW MODIFICATION UV systems validated with flow modification are less handicapped by required validation piping Systems that perform better during validation perform better in the field High-emitting low-pressure lamps can be used with minimal concern for reflection or chamber absorbance. Small communities can treat drinking water with UV systems containing fewer lamps Less Cost Less Maintenance Easy to Use

35 THANK YOU